1. Field of the Invention
A relatively high strain to failure composite explosion vent having ductile fracture behavior is provided for protecting a confined space from a high overpressure condition vent is especially adapted to cover relief openings in enclosures subject to rapid pressure build-ups that result from explosions or uncontrolled fires in a variety of structures and vessels including buildings, bag houses, tanks, grain silos, equipment, the duct work leading to the bag houses or to or from such equipment, and other structures subject to hazardous high overpressure events.
The vent includes an inner panel of thermoplastic synthetic resin reinforced with material that has a greater tensile strength than the resin. The reinforcing material preferably comprises woven glass fibers, plus optional random glass fibers. The panel has an elongated continuous groove that extends completely through or through only a portion of the thickness of the panel. Alternately, a series of individual end-to-end slots may be provided, each of which extends entirely through the panel or through only a portion of the panel. The groove or slots interrupt at least a part of the reinforcing material to define a line of weakness that presents a respective central relief area of the vent that opens under a high overpressure condition. Relatively thin cover sheets are provided on opposite sides of the central panel to enhance the fluid impermeability of the vent, permit use of the vent in applications that require sanitary components or equipment, and that function to provide relatively smooth opposed surface finishes for the vent. The groove or slots may be at least partially or completely filled with a synthetic resin material. Alternatively, an elongated object such as a steel wire may be embedded in the panel of a configuration defining the central relief opening in the vent that gives way and opens under a predetermined overpressure force.
The panel section of the vent may also be provided with elongated reinforcing components comprising glass fiber roving overlying the groove or certain of the line of weakness-defining slots. The reinforcing glass roving preferably extends across the full extent of the pressure relief area of the panel. The amount of overpressure required to open the relief area of the panel can be controlled by varying the number, configuration, glass composition, and relative orientation of the reinforcing components.
2. Description of the Prior Art
Explosion vents traditionally have been provided with a rupturable sheet of metal that has score lines or interrupted slits that define a line of weakness presenting the relief area of the vent. The amount of overpressure required to open the relief area of the vent is determined by, among other things, the shape of the line of weakness, the nature of the line of weakness, and the location of the line of weakness in the overall area of the vent.
An exemplary explosion vent is shown and described in U.S. Pat. No. 6,070,365, wherein a rectangular pressure relief panel is mounted in a frame adapted to be secured across a pressure relief opening. The unitary relief panel is formed from a single sheet of steel, stainless steel, Inconel, or other similar metal, and has a three-sided line of weakness defined by a plurality of interrupted slits. A series of spaced rupture tabs are often positioned over the line of weakness as shown in the '365 patent, that must rupture before the relief area of the panel gives away under a predetermined high overpressure resulting from an explosion or a fast-burning fire.
U.S. Pat. No. 5,036,632 is another example of a conventional rectangular metal sheet explosion vent that has a three-sided line of weakness defined by interrupted slits. Rupturable tabs are also provided in the vent of the '632 patent that must break before the central section of the panel ruptures along the slit line to relieve an overpressure. Elastomeric sealing gaskets may be provided around the periphery of the rupturable metal sheet.
U.S. Pat. No. 4,498,261, referred to in the disclosure of the '632 patent, is a rectangular vent panel that opens under a relatively low pressure in which the thin sheet structure is described as being medium impact polystyrene, a relatively soft metal such as aluminum alloy, or a fully annealed stainless steel. Interrupted X-pattern slits extend through the vent panel and define individual lines of weakness that terminate at the apex of the X. A thin sealing membrane having the same area as the rupture panel is adhesively bonded to the rupture panel, and may be formed of polyethylene, stainless steel, or aluminum. Similar structure is shown and described in U.S. Pat. No. 4,612,739.